Cobb - "What is the most resilient parasite? Bacteria? A virus? An intestinal worm? An idea. Resilient... Highly contagious. Once an idea has taken hold of the brain it's almost impossible to eradicate. An idea that is fully formed - fully understood - that sticks; right in there somewhere."
From my perspective that is the point of the film, it's a labyrinth you don't know if Cobbs dreaming or awake, does he even care? The producer left the conclusion of the film up to the viewer. I thought the children at the end were wearing the same clothes as they were when Cobb was dreaming..they wasn't. How much of anything do you consciously take in? The conscious mind takes in little it has to be focused, in comparison to the subconscious.
In the film it shows the never ending stairs puzzle, which does come to an end and the guy falls off. The stairs are the similar to the Penrose stairs quote from Wikipedia:- Penroses noted that "each part of the structure is acceptable as representing a flight of steps but the connections are such that the picture, as a whole, is inconsistent: The steps continually descend in a clockwise direction.
Escher also made a painting representing the Penrose stairs called Ascending and Descending, a further one called Waterfalls and another called Reality. All his paintings are definitely worth a look. Here are the stairs
